珊瑚钨锡矿硅质尾矿中Cd、As、Zn、F富集迁移及环境污染

硅质尾矿在释放中性矿山废水(NMD)时所伴生的多元素复合污染问题值得重视。本文以桂东北珊瑚矿尾矿作为研究对象,通过分析该尾矿的组构、元素富集及迁移特性,筛选出主要污染元素,并探讨尾矿胶结层对元素富集迁移的影响。结果表明:(1)该尾矿中Cd、As、Zn及F富集程度较高、可交换态含量(易迁移释放量)较大,是主要的污染元素,而Cu、Pb、Tl产生污染的可能性较小;(2)胶结层对重金属具有再富集作用,但其对可交换态Cd、As(Tl)再富集明显,而对可交换态Cu、Pb、Zn再富集则不明显。胶结层中次生伊利石、石膏等胶结物趋向于吸附富集活性可交换态Cd、As。这表明该尾矿可能迁移释放出含Cd、As浓度较高的NMD。研究表明,硅质尾矿风化释出NMD的同时,可能伴生Cd、As、Zn等重金属以及F的复合污染。

Enrichment, Migration and Environmental Effect of Cd, As, Zn, and F in Siliceous Tailings, Shanhu W-Sn mine, Guangxi Province, China

It should be paid attention to the issues of multi-elements compound pollution, associated with neutral mine drainage (NMD) from siliceous tailings which are rich in SiO₂ and poor in sulfide. This paper focuses on the siliceous tailings of Shanhu W-Sn mine, situated in the northeast of Guangxi Province, China. Through studying the fabrics and characteristics of enrichment and migration of Cu, Pb, Zn, Cd, Tl, As and F in the tailings, the paper intends to screen out main elements concerning environmental issues and investigate the influence of cementation layer in the tailings on enrichment and migration of the elements. Results show that (1) In Shanhu tailings, Cd, As, Zn and F are main pollution elements because they have higher enrichment degree and higher exchangeable fraction (i.e. easier migration release fraction), while Pb, Tl and Cu have lesser possibility of environmental pollution; (2) Cementation layer/hardpan has re-enrichment function to heavy metals, but exchangeable Cd, As (Tl) trend to concentrate in the hardpan, while exchangeable Cu, Pb and Zn do not have this concentration tendency. Secondary cements such as illite and gypsum in the hardpan may prefer to adsorb actively exchangeable Cd and As, which are extremely easy to remove, implying that Shanhu tailings may release higher concentrations of Cd and As. Therefore, Shanhu siliceous tailings possess a risk of Cd, As, Zn and F compound pollution, associated with NMD during tailings weathering.